Likeley Questions Flashcards
Name 3 rock properties that influence rock mechanical behaviour
Cleavage, hardness, solubility
Name 4 rock characteristics (describing a rock)
Type, age, place, structure
3 rock types
Igneous, sedimentary, metamorphic
Describe 3 occurrences of igneous rock
Plutonic - high pressure environment, slow cooling, intrusive plutons. Subvolcanic - transitional between intrusive sills and dykes. Volcanic - low pressure environment, fast cooling, extrusive.
3 types of igneous rock
Magma, volcanic, plutonic
3 volcanic processes
Lava, tephra, pyroclastic flows
What kind of rocks have the most desirable engineering properties and why
Intrusive and chrystallie extrusive rocks, they are strong, stable and little movement of water.
What can influence sedimentary rock characteristics
Type of material, transportation mechanism, depositional site
5 sedimentary rock groups
Clastic, bionic, chemical, volcaniclastic, mixed
Describe the general process of sedimentary rock
Weathering (from parent source ruck), erosion and transportation, deposition, accumulation, lithification.
Describe the lithification process
Soil into rock. Layers of soil, compaction, cementation, significant increase in strength.
Clastic classification
Clast composition, size, shape, sorting
Describe 3 metamorphic processes
Contact (high heat), dynamic ( deformation and pressure), regional (high heat and pressure).
How con crustal deformation occur
Tectonic movements, plutonic deposits and volcanic activity, charge in loading (gravity effects).
What can folding be effected by
Temperature, pressure, strain rate, rock type
Why does direction of bedding matter
Stability of structures, movement of water, tunnels and underground structures
4 planar defects
Fractures and joints, cleavage, bedding, lithologic boundaries.
Zonal defects
Crushed seam, sheared zone, infill, voids/cavities
Denudation
Process of exposing deposits. Weathering, erosion degradation, transportation - part of the exogenic process
Weathering types
Mechanical physical, chemical, biological.
When classifying rocks what would you write in the main paragraph?
Weathering, colour, fabric, rock name.
Unweathered
Rock mass shows no loss of strength, discolouration or other effects die to weathering. There may be slight discolouration on major rock mass defect surfaces or on clasts.
Completely weathered
Original rock strength is lost and the rock mass charged to a soil either by chemical decomposition or by physical disintegration.
What would you write in the qualifying paragraph
Strength, discontinuities, geologic information, characterises the rock mass
How could you determine strength (tests)
Unconfined compression test, point load test, rebound hammer
Discontinuities
Describe defects within the rock mass. Orientation, spacing, persistence, roughness, wall strength, aperature, infill, seepage, sets, block size and shape
ClassifyING roughness
Rough, smooth, slickensided. Stepped, undulating, planar.
Soil origins
Transported soils, residual soils, organic soils, volcanic soils
Transported soils
Alluvium ( rivers and streams clay to gravel size), colluvium (mass movement and surface water flow, clay to boulder size), glacial ( ice movement, silt to boulder size), aeolian (wind, silt size and fire sand), volcanic
Residual soils
Formed by weathering in place. Decomposition (chemical) disintegration (mechanical)
Organic soils
Formed in place by growth and decay of plants, accumulation of fragments of inorganic skeletons or shells of organisms. Low strength and stiffness.
Silts vs. Clays
Dilatant behaviour only occurs in silts. Shaking changes distribution of particles.
% gravel > % sand
Cu greater than 4 CC between 1 and 3
% sand > % Gravels
Cu greater than 6 and CC between 1 and 3 to be well graded
Hydrometer test
To determine the grain size distribution, better for fines clays and silts. Based on sedimentation and stokes law. Sampling approach, hydrometer approach,
2 tests for attenburg limits.
Casagrande apparatus,, liquid limit cone penetrometer.
Sand cone test
To find the bulk density / unit weight
Nuclear densometer
Density and water content measurement.
Fundamental seepage assumptions
- Flow is laminar,
- incompressible flow: conservation of mass,
- soil is saturated,
- flow is steady state.
Seepage is the difference in head between points needed for seepage to occur.
What effects the coefficient of permability
Void size, void continuity, soil particle shape, soil particle roughness, viscosity e density of water. Grain size distribution
Lab tests to determine K
Constant head test - coarse grained soils. Falling head test- course and five grained soils.
Constant head test
Head difference is constant.
Falling head rest
Head difference is changing,
Seepage parallel to layers
Head loss through each layer is the same, flow rate is split across layers. Hydraulic gradient I same - equivalent characteristics controlled by the most permeable layer.
Seepage normal to layers
Head loss through each layer varies. Flow rate is the same. Equivalent characteristics controlled by the most impermeable layer
Quick condition or piping
If upward seepage reduces effective stress, at some point seepage could reduce effective stress to zero or negative. No interparticle forces at this point, erosion will occur.
Tests to determine grain size distribution
Sieve analysis, hydrometer test
